Lithographic method, lithographic process and lithographic system

Abstract

A lithography method, a lithography process, and a lithography system are disclosed. The lithography method includes obtaining a relationship between a contamination layer thickness and a compensation energy, wherein the contamination layer is formed on a photomask and the compensation energy is capable of removing the contamination layer. The lithography method also includes obtaining a first thickness of a first contamination layer from a thickness measurement device, wherein the first contamination layer is formed on the photomask. The lithography method also includes applying a first compensation energy to light directed to the photomask, wherein the first compensation energy is calculated by the obtained relationship.

Description

TECHNICAL FIELD

[0001] Embodiments of the present disclosure relate to a lithography method, a lithography process, and a lithography system applying the lithography method or the lithography process. BACKGROUND

[0002] The semiconductor integrated circuit (IC) industry has experienced rapid growth. ICs have evolved from a technology using individual discrete components to a technology that uses a variety of very small ICs. The IC materials and design technology has progressed to a point where several generations of ICs are available, each generation having more complex circuitry and smaller components than the previous generation. During the evolution of ICs, the functional density (i.e., the number of interconnected devices per chip area) has generally increased while the geometry size (i.e., the smallest component (or line) that can be produced using a process) has decreased. This scaling down of the IC geometry size provides benefits in increasing the performance and lower costs of ICs.

[0003] For example, higher resolution lithography processes are needed. One lithography technology is extreme ultraviolet lithography (EUVL). Scanners used in EUVL use light in the extreme ultraviolet (EUV) region of the spectrum, which has a wavelength of about 1 to 100 nanometers. One type of EUV light source is a laser-produced plasma (LPP). LPP technology produces EUV light by focusing a high-energy laser beam onto a small droplet of target material to create a highly ionized plasma that emits EUV radiation with a peak emission at 13.5 nm. A collector then collects the EUV light and optical elements reflect the EUV light to a lithography exposure target, such as a substrate.

[0004] While the methods and apparatuses of lithography equipment are sufficient for their intended purposes, they can not meet all requirements. Therefore, to improve the critical dimension variation, how to reduce the contamination on the EUV mask is a problem to be solved. SUMMARY

[0005] According to one embodiment of the present disclosure, a lithography method includes obtaining a relationship between a contamination layer thickness and a compensation energy, wherein the contamination layer is formed on a mask and the compensation energy can remove the contamination layer. The lithography method also includes obtaining a first thickness of a first contamination layer from a thickness measuring device, wherein the first contamination layer is formed on the mask. The lithography method also includes applying a first compensation energy to light directed to the mask, wherein the first compensation energy is calculated by the aforementioned relationship.

[0006] According to another embodiment of the present disclosure, a lithography process includes performing a lithography process in a lithography system. The lithography system includes a first light source, a reticle stage, a substrate stage, and a thickness measurement device configured to measure a thickness of a contamination layer, wherein the contamination layer is formed on a reticle and the reticle is disposed on the reticle stage.

[0007] According to yet another embodiment of the present disclosure, a lithography system includes a light source, a reticle stage, a substrate stage, and a reticle storage. The reticle storage includes a plurality of storage units and a first thickness measurement device configured to measure a thickness of a contamination layer, wherein the contamination layer is formed on a reticle and the reticle is disposed in the reticle storage. BRIEF DESCRIPTION OF DRAWINGS

[0008] The subject matter of the present disclosure will be more readily understood with reference to the following implementation methods taken in conjunction with the accompanying drawings, in which like reference numerals designate identical items in the figures and, wherein:

[0009] Figure 1 According to some embodiments of the present disclosure, a schematic diagram of a lithography system is illustrated;

[0010] Figure 2 According to some embodiments of the present disclosure, a cross-sectional view of a reticle is illustrated;

[0011] Figure 3 According to some embodiments of the present disclosure, a graph illustrating a relationship between a contamination layer thickness and a critical dimension reduction is illustrated;

[0012] Figures 4A-4C According to some embodiments of the present disclosure, a graph illustrating how to use a compensation energy to reduce a critical dimension variation is illustrated;

[0013] Figures 5A-5B According to other embodiments of the present disclosure, a schematic diagram of a lithography system is illustrated;

[0014] Figure 6 According to some embodiments of the present disclosure, a top view of a reticle storage is illustrated.

[0015] SYMBOL DESCRIPTION

[0016] 10: lithography system

[0017] 12: radiation source / light source

[0018] 14: illuminator

[0019] 16: reticle stage

[0020] 18: reticle

[0021] 20: projection optical module / projection optical box

[0022] 22: pupil phase adjuster

[0023] 24: projection pupil plane

[0024] 26: substrate

[0025] 28: substrate stage

[0026] 30: light source

[0027] 32: detector

[0028] 40: substrate

[0029] 42: reflective multilayer film

[0030] 44: thin film

[0031] 46: thin film

[0032] 48: capping layer

[0033] 50: absorbing layer

[0034] 52: pattern

[0035] 54: backside conductive coating

[0036] 56: contamination layer

[0037] 80: controller

[0038] 101: load port

[0039] 102: transfer module

[0040] 104: transport stage

[0041] 105: process device

[0042] 105A: lithography chamber

[0043] 105B: device chamber

[0044] 105C: opening

[0045] 107: controller

[0046] 200: reticle

[0047] 250: light source

[0048] 260: projection optical module / projection optical box

[0049] 265: thickness measurement device

[0050] 270: axis

[0051] 300: reticle stage

[0052] 302: fitting line

[0053] 304: fitting line

[0054] 400: substrate

[0055] 402: line

[0056] 404: line

[0057] 406: line

[0058] 408: line

[0059] 600: reticle storage

[0060] 602: storage unit

[0061] 604: gantry

[0062] 606: track

[0063] 608: support

[0064] 610: robot arm

[0065] 612: stage

[0066] 614: thickness measurement device

[0067] 1021: control line

[0068] 1023: robot arm

[0069] 1051: substrate stage DETAILED DESCRIPTION

[0070] The following disclosure provides many different embodiments, or examples, for implementing different features of the disclosure. Some examples are provided in the following detailed description of the disclosure. Of course, it is to be understood that the following examples are merely described for the purposes of explanation. The examples are not intended to limit the disclosure. For example, if the following description states that a first structure is formed on or above a second structure, it is to be understood that this includes embodiments in which the first and second structures are directly in contact, as well as embodiments in which additional structures are formed between the first and second structures such that the first and second structures are not directly in contact. In addition, various examples of the disclosure can use repeated reference characters and / or numbers to describe various embodiments and / or aspects of the present disclosure. This repeated use of reference characters and / or numbers is for illustrative purposes, and does not limit the scope of the disclosure to the only embodiments for which it is used.

[0071] Moreover, spatially relative terms, such as "beneath", "below", "lower", "above", "upper", and the like, can be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. The spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. The devices can be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.

[0072] Figure 1 A schematic diagram of a lithography system 10 is depicted in accordance with some embodiments of the present disclosure. The lithography system 10 can be referred to as a scanner, and the configured scanner can perform corresponding lithography exposure processes depending on the radiation source and exposure mode. In some embodiments, the lithography system 10 is an extreme ultraviolet lithography (EUVL) system. For example, the lithography system 10 can be designed to use extreme ultraviolet (EUV) light or EUV radiation to expose photoresist. Photoresist is a material that is sensitive to light. The lithography system 10 uses a radiation source 12 to generate light, such as EUV light having a wavelength of about 1 nanometer to about 100 nanometers. In one example, the radiation source 12 generates EUV light having a wavelength of about 13.5 nanometers. Thus, the radiation source 12 can be an EUV radiation source 12.

[0073] The lithography system 10 also uses an illuminator 14. In some embodiments, the illuminator 14 includes various refractive optical elements, such as a single lens or a lens system having multiple lenses (zone plates), or the illuminator 14 includes various reflective optical elements (for EUV lithography systems), such as a single mirror or a mirror system having multiple mirrors. The illuminator 14 directs light from the radiation source 12 onto a reticle stage 16, and in particular onto a reticle 18 that is secured on the reticle stage 16. In the present embodiment, the radiation source 12 generates light having a wavelength in the EUV range, and the illuminator 14 uses reflective optical elements. In some embodiments, the illuminator 14 includes a dipole illumination component.

[0074] In some embodiments, illuminator 14 is operable to configure the mirrors to provide appropriate illumination to photomask 18. For example, the mirrors of illuminator 14 can be switched to reflect EUV light to different illumination positions. In some embodiments, the stage before illuminator 14 can additionally include other switchable mirrors that, together with the mirrors of illuminator 14, direct EUV light to different illumination positions. In some embodiments, illuminator 14 is configured to provide on-axis illumination (ONI) to photomask 18. In one example, a disk illuminator 14 with a partial coherence of at most 0.3 is used. In some other embodiments, illuminator 14 is configured to provide off-axis illumination (OAI) to photomask 18. In one example, illuminator 14 is a dipole illuminator. In some embodiments, the partial coherence of the dipole illuminator is at most 0.3.

[0075] Photomask stage 16 is configured to hold photomask 18. In some examples, photomask stage 16 includes an electrostatic chuck (e-chuck) to hold photomask 18. Since gas molecules absorb EUV, EUVL patterning systems are required to be maintained in a vacuum environment to avoid loss of EUV intensity. In this disclosure, the terms mask, photomask, and reticle are used interchangeably to refer to the same item. Photomask 18 will be described in more detail in Figure 2

[0076] Lithography system 10 can include a projection optics module (or projection optics box (POB) 20 arranged to image pattern 52 of photomask 18 onto substrate 26, which is held on substrate stage 28 of lithography system 10. In some embodiments, projection optics module 20 includes refractive optics (e.g., for ultraviolet (UV) lithography systems) or reflective optics (e.g., for EUV lithography systems). Light passes through photomask 18, creates different diffraction orders, and carries the image of pattern 52 to projection optics module 20. The magnification of projection optics module 20 is less than 1 (so that the imaged size on a target (e.g., substrate 26, described later) is smaller than the corresponding object size on photomask 18). Illuminator 14 and projection optics module 20 can be collectively referred to as the optics module of lithography system 10.

[0077] ​The lithography system 10 can include a pupil phase modulator 22 to modulate the phase of light directed from the reticle 18 so that the light has a phase distribution at the projection pupil plane 24. There is a plane in the optical module whose field distribution corresponds to the Fourier Transform of the object (in this case, the reticle 18). This plane is referred to as the projection pupil plane. The pupil phase modulator 22 provides a mechanism to modulate the phase of the light at the projection pupil plane 24. In some embodiments, the pupil phase modulator 22 includes a mechanism to adjust the mirrors of the projection optical module 20 to modulate the phase. For example, the mirrors of the projection optical module 20 are switchable and are controlled to reflect the EUV light, thereby modulating the phase of the light passing through the projection optical module 20.

[0078] In some embodiments, the pupil phase modulator 22 uses a pupil filter that is placed at the projection pupil plane 24. The pupil filter filters out certain spatial frequency components of the EUV light from the reticle 18. In particular, the pupil filter is a phase pupil filter that functions to modulate the phase distribution of the light that is directed through the projection optical module 20. However, phase pupil filters are limited in their use in some lithography systems, such as EUV lithography systems, because various materials absorb EUV light.

[0079] As previously described, the lithography system 10 also includes a substrate stage 28 to hold a substrate 26 to be patterned. The substrate 26 can be a semiconductor substrate. In some embodiments, the substrate 26 is a silicon substrate or other type of semiconductor substrate. The substrate is coated with a radiation-sensitive resist layer, in some embodiments, the radiation is, for example, extreme ultraviolet light.

[0080] Figure 2 A cross-sectional view of the reticle 18 is shown in accordance with some embodiments of the present disclosure. In some embodiments, the lithography system 10 is an EUVL system and the reticle 18 is a reflective reticle. As shown in FIG. 1, the reticle 18 includes a substrate 30 and a patterned layer 32 formed on the substrate 30. The patterned layer 32 includes a plurality of features 34. In some embodiments, the features 34 are formed by a plurality of lines 36. In some embodiments, the features 34 are formed by a plurality of lines 36 and a plurality of spaces 38. In some embodiments, the features 34 are formed by a plurality of lines 36 and a plurality of spaces 38, and the lines 36 and spaces 38 are arranged in a pattern. Figure 2As shown, the photomask 18 includes a substrate 40. The substrate 40 can be made of any suitable material, such as a low thermal expansion material (LTEM) or fused quartz. For example, the material of the substrate 40 includes titanium dioxide (Ti02), doped silicon dioxide (Si02), or other suitable material with a low coefficient of thermal expansion. The photomask 18 can further include a reflective multiple layer 42 deposited on the substrate 40. The reflective multiple layer 42 can include interleaved thin films 44 / 46. In some embodiments, the thin films 44 / 46 can include any suitable material that highly reflects EUV light. The photomask 18 can further include a capping layer 48, such as a ruthenium (Ru) formed capping layer 48, deposited on the reflective multiple layer 42 to provide a protective function. The photomask 18 can further include an absorber layer 50, such as a tantalum boron nitride (TaBN) layer, deposited on the reflective multiple layer 42. The absorber layer 50 has a pattern 52 to define an integrated circuit (IC) layer. In some embodiments, the photomask 18 includes a backside conductive coating 54. Alternatively, an additional reflective layer can be deposited on the reflective multiple layer 42 and this additional reflective layer is patterned to define the IC layer, thereby forming an EUV phase shift mask.

[0081] If the photomask 18 is not used in a process, a contamination layer 56 can form on top of the absorber layer 50 over time, as shown. Figure 1 The contamination layer 56 can include carbon and / or oxygen. For example, when the photomask 18 can be idle in a lithography process or in a photomask storage, the absorber layer 50 can be partially oxidized and the oxidized portion can form the contamination layer 56. When the photomask 18 with the contamination layer 56 is used in a process, the contamination layer 56 can cause a critical dimension reduction in EUV exposure. The contamination layer 56 can be removed by increasing the energy of the light emitted from the light source 12. However, in some other embodiments, if the thickness of the contamination layer 56 is thinner than expected, the high light energy can negatively affect the pattern formed on the substrate 26, and therefore, a dummy substrate is used when removing the contamination layer 56. To reduce the usage of the dummy substrate and thus improve the throughput, a thickness measurement device is configured in the lithography system 10.

[0082] Referring back to Figure 1 , the lithography system 10 further includes a light source 30 and a detector 32, as shown. Figure 1The light source 30 and the detector 32 can be part of a thickness measurement device to measure the thickness of the contamination layer 56 formed on the photomask 18. The device can be any suitable thickness measurement device. For example, the device can use ellipsometry to measure the thickness of the contamination layer 56 formed on the photomask 18. Ellipsometry is an optical technique that detects the properties of thin films and can be used to detect thickness or depth. After the incident light interacts with the contamination layer 56, a change in polarization can be used as an analytical signal. This is because the change in polarization varies with the thickness of the contamination layer 56. In some embodiments, the light source 30 can be a visible light source or a non-visible light source. For example, the light source 30 can be a laser. The light source 30 can generate light having one or more wavelengths, and the generated light can be directed to the photomask 18 and reflected from the photomask 18. The reflected light can be measured by the detector 32, and thus the thickness of the contamination layer 56 can be measured. Other components (not shown) of the thickness measurement device can include a polarizer and an analyzer.

[0083] The foregoing thickness measurement device uses ellipsometry to measure the thickness of the contamination layer 56. In some embodiments, the thickness measurement device can use other types of thickness measurement techniques, such as interferometry, reflectometry, picosecond ultrasonics, atomic force microscopy (AFM), scanning tunneling microscopy (STM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), or other suitable techniques.

[0084] The thickness measurement device (i.e., the light source 30 and the detector 32) is electrically connected to the controller 80, as shown in FIG. 1. The controller 80 can be a computer or other suitable device. The controller 80 can be used to control the thickness measurement device and to analyze the data collected by the thickness measurement device. For example, the controller 80 can be used to control the light source 30 to generate light having a desired wavelength or wavelengths. The controller 80 can also be used to control the light source 30 to direct the generated light to the photomask 18. The controller 80 can also be used to control the detector 32 to measure the reflected light from the photomask 18. The controller 80 can also be used to analyze the data collected by the detector 32 to determine the thickness of the contamination layer 56 formed on the photomask 18. Figure 3As shown. Controller 80 can control the thickness measuring device. Controller 80 can also be electrically connected to light source 12 to control the energy of the light emitted by light source 12. Controller 80 may have a processor, memory, transmitter, and receiver. In some embodiments, the configured controller 80 can collect and analyze thickness data from the thickness measuring device (i.e., light source 30 and detector 32) and determine whether to apply compensation energy to the light emitted by light source 12. Controller 80 can also determine how much compensation energy to apply to the light emitted by light source 12. For example, if the energy of the light emitted by light source 12 is set to X millijoules (mJ) and controller 80 decides to apply a component Y of compensation energy to the energy of the light emitted by light source 12, then controller 80 will increase the energy of the light emitted by light source 12 to X+Y mJ. Data obtained from different types of photomasks 18 can determine the amount of compensation energy.

[0085] Figure 3 A graph illustrating the relationship between the thickness of the contamination layer 56 and the amount of critical size reduction in the pattern, wherein the pattern is formed on the substrate 26, is plotted according to some embodiments of this disclosure. Figure 3 As shown, for a first type of photomask 18, such as a type A photomask, 10 data points show that an increase in the thickness of the contamination layer 56 leads to a reduction in the critical dimension (a positive number on the y-axis) in the pattern, where the pattern is formed on the substrate 26 using a first type of photomask 18. Fitted line 302 shows a first relationship between the thickness of the contamination layer 56 and the amount of reduction in the critical dimension. For a second type of photomask 18, such as a type B photomask, 10 data points show that an increase in the thickness of the contamination layer 56 leads to a reduction in the critical dimension in the pattern, where the pattern is formed on the substrate 26 using a second type of photomask 18. Fitted line 304 shows a second relationship between the thickness of the contamination layer 56 and the amount of reduction in the critical dimension. Figure 1 As shown, the first relationship differs from the second relationship. Therefore, the relationship between the contaminant layer 56 thickness and the critical size reduction may differ for different types of photomasks 18. The relationship may be linear, quadratic, cubic, or other suitable. In some embodiments, for certain types of photomasks 18, the relationship between the contaminant layer 56 thickness and the critical size reduction is y = K / (1 + be). -ax ), where x is the thickness of the contamination layer 56, a, b, and K are constants of the adaptation line (e.g., adaptation line 302 or 304), and y is the critical size reduction.

[0086] After the relationship between the thickness of the contaminant layer 56 and the critical dimension reduction in each type of reticle 18 is confirmed, the relationship between the critical dimension reduction and the compensation energy can be determined. For example, the relationship between the critical dimension reduction and the compensation energy can be that 1 mJ of compensation energy is applied for each 1 nm of critical dimension reduction. In some embodiments, the relationship between the critical dimension reduction and the compensation energy is y = x, where y is the compensation energy and x is the critical dimension reduction. In this case, the relationship between the thickness of the contaminant layer 56 and the compensation energy for one type of reticle 18 is y = K / (l + be -ax ), where x is the thickness of the contaminant layer 56, a, b, and K are constants of the fit line (e.g., the fit line 302 or 304), and y is the compensation energy.

[0087] Referring back to Figures 4A-4C , the relationship between the thickness of the contaminant layer 56 and the compensation energy to be applied is stored in the controller 80, which can use the thickness information and the aforementioned relationship to regulate the energy of the light emitted by the light source 12. For example, the controller 80 receives a signal from the thickness measurement device (i.e., the detector 32) and analyzes the thickness of the contaminant layer 56. Based on the relationship stored in the controller 80, such as the relationship y = K / (l + be -ax ) where x is the thickness of the contaminant layer 56 and a, b, and K are constants of the fit line, the controller 80 can calculate the value of the compensation energy y. The controller 80 then regulates the light source 12 to increase the energy of the light emitted by the light source 12, and the amount of increase can be equal to the compensation energy y. After the compensation energy is applied, the contaminant layer 56 can be removed when the light emitted by the light source 12 reaches the reticle 18. In some embodiments, the thickness of the contaminant layer 56 is measured before the substrate 26 is processed. For example, the thickness measurement device is used to confirm whether the contaminant layer 56 is formed on the reticle 18 before the substrate 26 is processed, and if the contaminant layer 56 is formed on the reticle 18, the thickness of the contaminant layer 56 is measured. When the thickness of the contaminant layer 56 is greater than a threshold value, the compensation energy is applied to the light emitted by the light source 12 during processing of the substrate 26. The thickness measurement device can be used before each substrate 26 is processed. The thickness measurement device can perform in-situ detection of the reticle 18. In some embodiments, the thickness of the contaminant layer 56 can be measured before a group (batch) of substrates 26 is processed.

[0088] Figure 4A A graph showing how compensation energy is used to reduce the critical dimension variation in a group of substrates (e.g., the substrates 26) according to some embodiments of the present disclosure is shown. As Figure 1As shown, a set of substrates 26, or a set of wafers, is operated with the reticle 18 without using compensation energy. The set of substrates 26 can include any number of substrates 26 greater than one. In some embodiments, the set of substrates 26 includes 151 substrates. The critical dimensions of the substrates 26 are indicated by line 402. The line 402, i.e., the critical dimensions of the pattern on the substrates 26, has a high standard deviation (three standard deviations (3σ) of about 0.31). Specifically, the critical dimension of the first wafer is smaller because the reticle 18 is in an idle state (e.g., the reticle 18 is stored in a reticle storage 600 (see Figure 1 ) before being moved into the lithography chamber), the critical dimension of the 19th wafer is smaller because the reticle 18 is idle for about 8 hours, the critical dimension of the 121st wafer is smaller because the reticle 18 is idle for about 41 hours, and the critical dimension of the 151st wafer is smaller because the reticle 18 is idle for about 11 hours. As previously described, the reticle 18 in an idle state is the cause of the formation of the contamination layer 56. The contamination layer 56 can cause the critical dimensions of the pattern on the substrates 56 to decrease. Because the four data points described above exhibit smaller critical dimensions, the overall consistency of the critical dimensions of this set of substrates 26 decreases (i.e., higher standard deviation). The behavior pattern of the critical dimensions of a particular type of reticle 18 will be stored in the controller 80 (see Figure 4B ) in the form of line 402.

[0089] Figure 3 According to some embodiments of the present disclosure, how compensation energy is used is illustrated. With the relationship between the thickness of the contamination layer 56 in a particular reticle 18 and the compensation energy known (e.g., the relationship is y = K / (l + be -ax where x is the thickness of the contamination layer 56, a, b, and K are constants of a fitted line (e.g., the fitted line 302 or 304 of Figure 6 ), and y is the compensation energy), the light emitted by the light source 12 can be subjected to compensation energy while one or more substrates 26 of a set of substrates 26 are being operated. The right y-axis corresponds to line 404, which indicates the idle time of the reticle 18. The idle reticle 18 can be in the lithography system 10 or the reticle storage 600 (see Figure 1 ). The left y-axis corresponds to line 406, which indicates the compensation energy applied. For example, the reticle 18 is idle for about 11 hours before the first substrate 26 is operated, and the thickness of the contamination layer 56 formed on the reticle 18 is measured using the thickness measurement device (i.e., the light source 30 and the detector 32) before the first substrate 26 is operated. From the thickness of the contamination layer 56 and the relationship between the thickness of the contamination layer 56 and the compensation energy, the controller 80 (see Figure 1 ) can control the light source 12 (see Figure 4A ) to emit light that has been subjected to compensation energy. The compensation energy applied can be found in line 406, which exhibits a decreasing trend to 0. The decreasing pattern is based on the relationship between the thickness of the contamination layer 56 and the compensation energy.Figure 1 The behavior of the critical dimension exhibited by the centerline 402. The critical dimension of the substrates 26 increased as the substrates 26 were processed, which indicates that the light emitted by the light source 12 without the application of the compensation energy can gradually remove the contamination layer 56. Thus, the decreasing trend of the compensation energy can avoid a sudden increase in the critical dimension and help remove the contamination layer 56.

[0090] The controller 80 can determine when to apply the compensation energy to the light emitted by the light source 12 (see Figure 4A ) based on the stored behavior of the critical dimension. For example, the line 402 (see Figure 4C ) shows that the photomask 18 was idle for about 8 hours before the 19th substrate 26 was processed, and the critical dimension of the 19th substrate 26 was substantially reduced. The 8 hours of idling caused the contamination layer 56 to form on the photomask 18, and thus, to gradually remove this contamination layer 56, the controller 80 applied the compensation energy to the light when the 19th substrate 26 was processed. Likewise, to remove the contamination layer 56 and at the same time not cause a sudden increase in the critical dimension, the compensation energy will gradually decrease to 0.

[0091] Likewise, the photomask 18 was idle for about 41 hours before the 121st substrate 26 was processed and the contamination layer 56 formed during the 41 hours of idling, and thus, to gradually remove this contamination layer 56, the controller 80 applied the compensation energy to the light when the 121st substrate 26 was processed. Next, the photomask 18 was idle for about 11 hours before the 151st substrate 26 was processed and the contamination layer 56 formed during the 11 hours of idling, and thus, to gradually remove this contamination layer 56, the controller 80 applied the compensation energy to the light when the 151st substrate 26 was processed.

[0092] Figure 4B A graph of the variation of the critical dimension in a set of substrates (e.g., the substrates 26) using the compensation energy according to the method described above is shown according to some embodiments of the present disclosure. As shown, the critical dimension of the substrates 26 is denoted by the line 408. The line 408 (i.e., the critical dimension of the pattern on the substrates 26) has a lower standard deviation (about 0.20 for three standard deviations (3σ)) than the standard deviation of the line 402 (see Figure 4C ). Figure 4A Figures 4A-4C

[0093] Figures 5A-5B ​​The illustrated embodiment illustrates a method in which the thickness of the contamination layer 56 formed on the reticle 18 is measured prior to processing a group of substrates 26. If the thickness of the contamination layer 56 is greater than a threshold value, compensation energy is applied during processing of a first subgroup of substrates 26, and the compensation energy will be gradually reduced to zero. The critical dimension variation data for which no compensation energy is applied is stored in the controller 80, and subsequently, the controller 80 can determine when to apply compensation energy based on the stored critical dimension variation data. In other words, the thickness measurement device is used only once for each group of substrates 26.

[0094] Figure 5A According to other embodiments of the present disclosure, a schematic diagram of a lithography system 10 is illustrated. In some embodiments, as Figure 1 In the illustrated embodiment, the lithography system 10 includes a load port 101, a transferring module 102, a transport stage 104, a processing device 105, and a controller 107. The components of the lithography system 10 can be added or omitted without limitation of the embodiments of the present disclosure. In some embodiments, the lithography system 10 is an EUVL system and the processing device 105 is an EUVL device.

[0095] The transferring module 102 is configured to transfer the reticle 200 between the load port 101 and the transport stage 104. The reticle 200 can be Figure 5A The illustrated reticle 18. In some embodiments, the transferring module 102 is disposed between the load port 101 and the transport stage 104. The transferring module 102 can include a control circuit 1021 and a robot manipulator 1023. The control circuit 1021 is configured to generate an electronic signal to the robot manipulator 1023, thereby controlling the robot manipulator 1023 to transfer the reticle 200. In some embodiments, the robot manipulator 1023 can include a six-axis robot manipulator configured to hold the reticle 200.

[0096] In some embodiments, the transport stage 104 is used to transport the reticle 200 into the processing device 105. As Figure 1 As illustrated, the processing device 105 can include a lithography chamber 105A and a device chamber 105B. One or more openings 105C are formed on a chamber wall, in which the chamber wall separates the lithography chamber 105A and the device chamber 105B. The lithography chamber 105A can include a reticle stage 300, a substrate stage 1051 to support a substrate 400, and a projection optics module 260 (or referred to as a projection optics box (POB)). The substrate 400 can be the substrate 26, the reticle stage 300 can be the reticle stage 16, the substrate stage 1051 can be the substrate stage 28, and the projection optics module 260 can be the projection optics module 20, asFigure 1 The.

[0097] In some embodiments, as Figure 1 shown, a light source 250 and a thickness measurement device 265 are disposed within the device chamber 105B. The light source 250 can be a radiation source 12 as Figure 1 shown, and the thickness measurement device 265 can be a thickness measurement device as Figure 5A described (i.e., the light source 30 and the detector 32). In some embodiments, the thickness measurement device 265 includes a light source, a detector, and other elements (e.g., light source elements). The thickness measurement device 265 is configured to measure the thickness of the contamination layer 56 formed on the reticle 200 in-situ. The thickness measurement device 265 operates in the same manner as the thickness measurement device as Figure 5B described. The reticle stage 300 is coupled to an axis 270 configured to tilt the reticle stage 300 with respect to a reference plane that is substantially parallel to the top surface of the substrate stage 1051. Figure 5A The position of the reticle stage 300 is configured for the lithography process in which light emanates from the light source 250, then the light reaches the reticle 200 and reflects to the substrate 400. In Figure 5B the embodiments shown, the tilted reticle stage 300 is directed toward the thickness measurement device 265 to allow the thickness measurement device 265 to measure the thickness of the contamination layer 56 on the reticle 200. Tilting the reticle stage 300 by the axis 270 allows the light source and the detector of the thickness measurement device 265 to remain in the same position. Prior to processing each substrate 400 or a group of substrates 400, the reticle stage 300 can be tilted to allow the thickness measurement device 265 to measure the reticle 200.

[0098] As Figure 1 and Figure 6 shown, the lithography system 10 can further include a controller 107 to control the operation of the lithography system 10. The controller 107 can be a controller 80 as Figure 6 described. In some embodiments, the controller 107 receives the thickness of the contamination layer 56 on the reticle 200 from the thickness measurement device 265 and controls the light source 250 such that a compensation energy can be applied to the light emitted by the light source 250 to remove the contamination layer 56. As previously described, the thickness measurement device 265 can be used to measure the reticle 200 prior to processing each substrate 400 or a group of substrates 400.

[0099] Figure 5A A top view of a reticle storage 600 is shown according to some embodiments of the present disclosure. The reticle storage 600 can be part of the lithography system 10. As Figure 5BAs shown, the reticle library 600 includes an array of one or more storage units 602. Each storage unit 602 can be configured to store one or more reticles 18 (or reticles 200). A gantry 604 is disposed above the space between the array of storage units 602. The gantry 604 includes a rail 606 supported by a support 608. A robotic arm 610 is configured on the rail 606 of the gantry 604. The configured robotic arm 610 can transport the reticles 18 into and out of the reticle library 600. The reticle library 600 further includes a stage 612 and a thickness measurement device 614. Prior to the reticle 18 being placed in the process device 105 (see Figure 5A and Figure 5B ), the reticle 18 (or reticle 200) can be placed on the stage 612 using the robotic arm 610 and the thickness measurement device 614 measures the thickness of the contaminant layer 56 formed on the reticle 18. The thickness measurement device 614 can be the thickness measurement device 265 as described in Figure 1 and Figure 5B . The thickness measurement device 614 can be electrically connected to a controller, such as the controller 80 or the controller 107, and transmit the thickness data to the controller. With the thickness of the contaminant layer 56 known, the controller can apply a compensating energy to the light to remove the contaminant layer 56 from the reticle 18.

[0100] The thickness measurement device (e.g., the light source 30 and the detector 32, see Figure 6 ), the thickness measurement device 265 (see FIG. 5A and Figure 1 ), or the thickness measurement device 614 (see Figure 5A ) can be used to measure the thickness of the contaminant layer 56 formed on the reticle 18 (or reticle 200). Prior to and / or during the operation of each substrate 26 (or substrate 400) or each group of substrates 26 (or substrate 400), a compensating energy can be applied to the light to remove the contaminant layer 56 from the reticle 18 (or reticle 200). The thickness of the contaminant layer 56 can be measured in the process device as shown in Figure 5B , Figure 6 and Figure 5A or in the reticle library 600 as shown in Figure 5B . The thickness of the contaminant layer 56 can be measured at any location along the way the reticle 18 (or reticle 200) is moved from the reticle library 600 to the process device. In some embodiments, the thickness measurement device can be disposed on the transport stage 104 (see ​ and ​ ). In some embodiments, multiple thickness measurement devices are disposed along the transport path of the reticle 18. For example, the thickness measurement device 614 and the thickness measurement device 265 can be used simultaneously.

[0101] Various embodiments of the present disclosure provide a lithography system including a thickness measurement device to measure a thickness of a contaminant layer formed on a reticle. The thickness measurement device can be disposed in a process device or a reticle library. The thickness data can be converted to a compensation energy signal, and the compensation energy can be applied to the light before each exposure (between substrates) or each set of exposures (between batches). Some embodiments can have advantages. For example, variability in critical dimensions can be improved. Furthermore, the use of a dummy substrate is eliminated, thereby improving throughput.

[0102] One embodiment provides a lithography method. The lithography method includes obtaining a relationship between a thickness of a contaminant layer and a compensation energy, where the contaminant layer is formed on a reticle and the compensation energy removes the contaminant layer. The lithography method also includes obtaining a first thickness of a first contaminant layer from a thickness measurement device, where the first contaminant layer is formed on the reticle. The lithography method also includes applying a first compensation energy to light directed to the reticle, where the first compensation energy is calculated from the aforementioned relationship.

[0103] In some embodiments, the lithography method further includes measuring the first thickness of the first contaminant layer using the thickness measurement device. In some embodiments, the first thickness of the first contaminant layer is measured in a process device. In some embodiments, the first thickness of the first contaminant layer is measured in a reticle library. In some embodiments, the lithography method further includes forming a second contaminant layer on the reticle after applying the first compensation energy, where the second contaminant layer is formed during a period of time that the reticle is idle. In some embodiments, the period of time is greater than about 8 hours. In some embodiments, the reticle is disposed in a lithography system during the period of time that the reticle is idle. In some embodiments, the lithography method further includes applying a second compensation energy to second light directed to the reticle, where the second compensation energy is calculated from the aforementioned relationship. In some embodiments, the first compensation energy is different than the second compensation energy.

[0104] Another embodiment provides a lithography process. The process includes performing a lithography process in a lithography system. The lithography system includes a first light source, a reticle stage, a substrate stage, and a thickness measurement device disposed to measure a thickness of a contaminant layer, where the contaminant layer is formed on a reticle and the reticle is disposed on the reticle stage.

[0105] In some embodiments, the thickness measurement device includes a second light source and a detector. In some embodiments, the lithography process further includes an illuminator disposed between the first light source and the reticle stage, a projection optics box disposed between the reticle stage and the substrate stage, and a controller electrically connected to the first light source, the second light source, and the detector. In some embodiments, the reticle stage and the substrate stage are disposed in a lithography chamber, and the first light source and the thickness measurement device are disposed in a device chamber adjacent to the lithography chamber. In some embodiments, the lithography process further includes a transfer module and a transport stage, wherein the transport stage is disposed between the transfer module and the lithography chamber. In some embodiments, the lithography process further includes a shaft coupled to the reticle stage, wherein the shaft is configured to tilt the reticle stage about a plane substantially parallel to a top surface of the substrate stage. In some embodiments, the lithography process is an extreme ultraviolet lithography process.

[0106] Another embodiment provides a lithography system. The lithography system includes a light source, a reticle stage, a substrate stage, and a reticle storage. The reticle storage includes a plurality of storage units and a first thickness measurement device configured to measure a thickness of a contamination layer, wherein the contamination layer is formed on a reticle and the reticle is disposed in the reticle storage.

[0107] In some embodiments, the lithography system further includes an illuminator disposed between the light source and the reticle stage, a projection optics box disposed between the reticle stage and the substrate stage, and a controller electrically connected to the light source and the first thickness measurement device. In some embodiments, the reticle stage and the substrate stage are disposed in a lithography chamber, and the light source is disposed in a device chamber adjacent to the lithography chamber. In some embodiments, the lithography system further includes a second thickness measurement device disposed in the device chamber, wherein the second thickness measurement device is electrically connected to the controller.

[0108] The foregoing outlines features of several embodiments of the present disclosure so that those skilled in the art can better understand the present disclosure. Any features described as being in accordance with the present disclosure are thus intended to be within the scope of the present disclosure. Any features described as being in accordance with the present disclosure are thus intended to be within the scope of the present disclosure. Any features described as being in accordance with the present disclosure are thus intended to be within the scope of the present disclosure. Any features described as being in accordance with the present disclosure are thus intended to be within the scope of the present disclosure. Any features described as being in accordance with the present disclosure are thus intended to be within the scope of the present disclosure. 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Claims

1. A lithography method, characterized by, comprising: obtaining a relationship between a thickness of a first contamination layer and a compensation energy, wherein the first contamination layer is formed on a photomask and the compensation energy removes the first contamination layer; obtaining a first thickness of a first contamination layer from a thickness measuring device, wherein the first contamination layer is formed on the photomask; and applying a first compensation energy to a first light directed to the photomask to remove the first contamination layer, wherein the first compensation energy is calculated by the relationship, wherein the first compensation energy is a decreasing compensation energy to remove the first contamination layer during a lithography process.

2. The lithography method of claim 1, wherein, further comprising measuring the first thickness of the first contamination layer using the thickness measuring device.

3. The lithography method of claim 2, wherein, measuring the first thickness of the first contamination layer in a process device.

4. The lithography method of claim 2, wherein, measuring the first thickness of the first contamination layer in a photomask storage.

5. The lithography method of claim 1, wherein, further comprising forming a second contamination layer on the photomask after applying the first compensation energy, wherein the second contamination layer is formed during a time the photomask is left idle.

6. The lithography method of claim 5, wherein, the time is greater than 8 hours.

7. The lithography method of claim 5, wherein, during the photomask is left idle, the photomask is disposed in a lithography system.

8. The lithography method of claim 7, wherein, further comprising applying a second compensation energy to a second light directed to the photomask, wherein the second compensation energy is calculated by the relationship.

9. The lithography method of claim 8, wherein, the second contamination layer is removed by the second compensation energy.

10. A lithographic process, characterized by, comprising: performing the lithography process in a lithography system, wherein the lithography system comprises: a first light source; a photomask stage; a substrate stage; a thickness measuring device disposed to measure a thickness of a contamination layer, wherein the contamination layer is formed on a photomask and the photomask is disposed on the photomask stage; a controller disposed to control light emitted by the first light source, and the light emitted by the first light source has a decreasing compensation energy to remove the contamination layer during the lithography process.

11. The lithographic process of claim 10, wherein, the thickness measuring device comprises a second light source and a detector.

12. The lithographic process of claim 11, wherein, further comprising: an illuminator disposed between the first light source and the photomask stage; and a projection optics box disposed between the photomask stage and the substrate stage. the photomask stage and the substrate stage are disposed in a lithography chamber, and the first light source and the thickness measuring device are disposed in a device chamber adjacent to the lithography chamber.

13. The lithographic process of claim 10, wherein, further comprising a transfer module and a transport stage, wherein the transport stage is disposed between the transfer module and the lithography chamber.

14. The lithographic process of claim 13, wherein, further comprising a shaft coupled to the photomask stage, wherein the shaft is disposed to tilt the photomask stage to a plane substantially parallel to a top surface of the substrate stage.

15. The lithographic process of claim 13, wherein, the lithography process is an extreme ultraviolet lithography process.

16. The lithographic process of claim 10, wherein, comprising:

17. A lithography system, comprising: a light source disposed to expose a photoresist layer; a photomask stage; a substrate stage; a photomask storage comprising: a plurality of storage units; and a first thickness measuring device disposed to measure a thickness of a contamination layer, wherein the contamination layer is formed on a photomask and the photomask is disposed in the photomask storage; and a controller disposed to control light emitted by the light source, and the light emitted by the light source has a decreasing compensation energy to remove the contamination layer during a lithography process. further comprising:

18. The lithography system of claim 17, wherein, ​ a light source configured to emit light; a light source configured to emit light; 19. The lithography system of claim 18, wherein, a projection optics box disposed between the mask table and the substrate table.

20. The lithography system of claim 19, wherein, The mask table and the substrate table are disposed in a lithography chamber, and the light source is disposed in a device chamber adjacent to the lithography chamber. Further comprising a second thickness measuring device disposed in the device chamber, wherein the second thickness measuring device is electrically connected to the controller.

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